SEVASTOPOL, June 17. /TASS/. Ships and submarines that will enter service with the Russian Black Sea Fleet will eventually undergo upgrade and maintenance at the Sevastopol Sea Plant that previously belonged to Ukrainian billionaire President Petro Poroshenko, Plant Director Alexander Yuryev said on Wednesday.

The Sevastopol Sea Plant has recently been turned into a state unitary enterprise, the director said.

"After the arrival of Project 636 submarines and the expiry of their warranty period operation, repairs will be held here. The corvettes under construction at the Yantar shipyard will undergo modernization and repairs at our plant. This has already been decided," he said.

The Russian Black Sea Fleet is to get six Project 636.3 Varshavyanka-class submarines before the autumn of 2016. The first two submarines dubbed Novorossiysk and Rostov-on-Don were already transferred to the Navy last year. So far, they are undergoing deep-water tests in Russia’s Northern Fleet.

The third submarine dubbed Stary Oskol will be handed over the Navy during the international naval show in St. Petersburg in July.

The Sevastopol Sea Plant, formerly known as the Lazarev Admiralty, was founded in 1783. This largest ship-building enterprise in Sevastopol has three dry docks.

During the Soviet period, the Sevastopol Sea Plant was among the world’s leaders in the construction of crane vessels but actually ground to a halt by 2010, keeping only 200 workers out of the 16,000 workforce.

The Sevastopol Sea Plant was placed under full control of Ukrprominvest Group owned by Poroshenko in December 2010.

After Crimea’s reintegration into Russia, the Sevastopol government took a decision in February 2015 to place the enterprise into state ownership.